Essays on physical and financial well-being in low- and middle-income countries

Many socio-economic factors are threatening the physical, mental, and financial well-being among the population residing in low- and middle-income countries, including financial stress, discrimination, violence, health issues, and inequalities. In the five chapters of my dissertation, I exploit experimental or quasi-experimental natures of socio-economic shocks in China, Peru and Uganda, to measure their impacts on the physical and financial well-being on individuals. The first chapter of this dissertation provides information on the study background, the data and presents an overview of each chapter. The remainder of the dissertation consists of five essays stretching out over the next chapters. China is well-known for its skewed sex ratios and huge demographic imbalance. In the first chapter, I exploit a cross-cohort spatial comparison to analyze the impact of demographic imbalance on the payment of brideprices and dowries in China. This chapter exploits the variation of sex ratios exposed to children born in the same natal family but born in different years. I use a difference-in-difference estimation and provide the very first empirical evidence that an increase in male surplus leads to higher incidence and value of brideprices, but it has no effect on dowries. Subsequent investigations reveal that brideprices and dowries carry different significance in the Chinese society, which explains the co-existence and co-development of both payments in the 21st century. Chapter 3 analyzes the negative health impact of rising housing prices in China. There is massive housing price appreciation since the early 2000s, which caused huge financial stress to households because of the strong social norm of owning rather than renting a house or apartment. We highlight that the high competition among males in the marriage market due to the “missing women” phenomenon is an important factor that contributes to such a negative health effect. Chapter 4 shows that natural disasters would elevate the incidence of intimate partner violence through higher alcohol use by the male partner, higher likelihood of co-residing with the male partner, and an increase in male intra-household economic power. Moreover, we highlight that the access to protective institutions, such as the “women justice centers”, are of vital importance to women’s vulnerability of intra-household violence. This paper points out one important but often neglected socio-economic consequence of natural disasters, and provides a strong policy implication for the post-disaster relief and reconstruction. The last two chapters are based on data collected in Uganda. The fourth chapter evaluates the impact of a financial education program on the use of digital finance (mobile money) as well as the business performance and household finance among microentrepreneurs in rural Uganda. We design a randomized saturation experiment, and find a positive impact of financial education on the use of mobile money, saving promotion, and business investments on targeted entrepreneurs. At the same time, we do not find evidence of positive spillover effects on the untreated ones in treated clusters. Instead, the estimated spillover coefficients often show negative (albeit insignificant) signs. In the last chapter, we document that the COVID-19 lockdown increases the financial stress of the micro-entrepreneurs in rural Uganda in the long term

MBAR-enhanced lattice Monte Carlo simulation of the effect of helices on membrane protein aggregation

We study the effect of helical structure on the aggregation of proteins using a simplified lattice protein model with an implicit membrane environment. A recently proposed Monte Carlo approach, which exploits the proven statistical optimality of the MBAR estimator in order to improve simulation efficiency, was used. The results show that with both two and four proteins present, the tendency to aggregate is strongly expedited by the presence of amphipathic helix (APH), whereas a transmembrane helix (TMH) slightly disfavours aggregation. When four protein molecules are present, partially aggregated states (dimers and trimers) were more common when the APH was present, compared with the cases where no helices or only the TMH is present

Advances in Monte Carlo techniques with application to lattice protein aggregation

Motivated by an intricate mechanism to transport folded proteins across biological membranes, known as the Twin-arginine translocation (Tat) pathway, we construct lattice protein models in an attempt to study the aggregation of the membrane protein TatA, which plays an integral role during active Tat translocation. We develop force field that characterizes intra- and inter-residue interactions, as well as how each residue interacts with its environment. Although written with the Tat process in mind, this thesis is mainly devoted to developing efficient Monte Carlo schemes for biomolecular simulations, which are often challenged and impeded by complex energy landscapes. To tackle the local trap problem that is typical in Metropolis sampling, the idea of dynamic weighting is incorporated into the parallel tempering (PT) algorithm. Our results show that, when applied to the lattice-protein model, the modified PT algorithm is capable of locating the low energy state much more quickly, but does not produce reliable estimates for equilibrium expectations. A modern method for free energy calculation, called the multistate Bennett acceptance ratio (MBAR) estimator, is reviewed from a statistical perspective, reminiscent of the underlying statistical theory which the method is based upon. Instead of adopting the common practice of using MBAR as a post-simulation analysis tool, we propose a new approach that integrates MBAR into simulation, allowing the simulation to benefit from the statistical optimality of the MBAR estimator. We show that the MBAR-enhanced Monte Carlo improves simulation efficiency of the lattice-protein aggregation model and, since it can also be applied to continuous models, provides a promising alternative to the study of more realistic systems. The new method is then applied to our model of TatA, where the protein features both a transmembrane and an amphipathic helix. The effect of individual helices on dimerization was studied and problem with the move set was identified. In this thesis, we used pull move and translation move as our Monte Carlo trial moves. Implementation details of pull moves, which are often omitted by many researchers who use them for sampling configuration space, are given in Chapter 1. We show that, for our double-helix TatA model, pull moves are no longer efficient moves and therefore, for future study of more realistic systems, we point to several methods which all attempt to design efficient trial moves. Aggregation of more than two polymer chains was also considered in this thesis

Simultaneously Transmitting and Reflecting Surface (STARS) for Terahertz Communications

A simultaneously transmitting and reflecting surface (STARS) aided terahertz (THz) communication system is proposed. A novel power consumption model is proposed that depends on the type and resolution of the STARS elements. The spectral efficiency (SE) and energy efficiency (EE) are maximized in both narrowband and wideband THz systems by jointly optimizing the hybrid beamforming at the base station (BS) and the passive beamforming at the STARS. 1) For narrowband systems, independent phase-shift STARSs are investigated first. The resulting complex joint optimization problem is decoupled into a series of subproblems using penalty dual decomposition. Low-complexity element-wise algorithms are proposed to optimize the analog beamforming at the BS and the passive beamforming at the STARS. The proposed algorithm is then extended to the case of coupled phase-shift STARS. 2) For wideband systems, the spatial wideband effect at the BS and STARS leads to significant performance degradation due to the beam split issue. To address this, true time delayers (TTDs) are introduced into the conventional hybrid beamforming structure for facilitating wideband beamforming. An iterative algorithm based on the quasi-Newton method is proposed to design the coefficients of the TTDs. Finally, our numerical results confirm the superiority of the STARS over the conventional reconfigurable intelligent surface (RIS). It is also revealed that i) there is only a slight performance loss in terms of SE and EE caused by coupled phase shifts of the STARS in both narrowband and wideband systems, and ii) the conventional hybrid beamforming achieves comparable SE performance and much higher EE performance compared with the full-digital beamforming in narrowband systems but not in wideband systems, where the TTD-based hybrid beamforming is required for mitigating wideband beam split.Comment: 17 pages, 12 figure

Can Deep Learning Approach Be Virtually Cultivated Via Social Learning Network

With the development of information technology especially kinds of social interaction techniques, social learning networks as a new platform have changed students’ learning behaviors and improve their learning performance. However, how this change happens especially how social learning networks change students’ learning approaches were not very clear. To address this gap, in this research, we try to investigate the impacts of social learning network on students’ learning approaches by conducting an experiment. In the experiment, students were randomly divided into two groups: control group and experimental group. We try to investigate the differences of students’ leaning behavior in terms of learning approaches in the two groups. We also present the theoretical, practical implications and future research

Near-Field Communications: What Will Be Different?

The design dilemma of "What will be different between near-field communications (NFC) and far-field communications (FFC)?" is addressed from four perspectives. 1) From the channel modelling perspective, the differences between near-field and far-field channel models are discussed. A novel Green's function-based channel model is proposed for continuous-aperture antennas, which is contrasted to conventional channel models tailored for spatially-discrete antennas. 2) From the performance analysis perspective, analytical results for characterizing the degrees of freedom and the power scaling laws in the near-field region are provided for both spatially-discrete and continuous-aperture antennas. 3) From the beamforming perspective, far-field beamforming is analogous to a "flashlight" that enables beamsteering, while near-field beamforming can be likened to a "spotlight" that facilitates beamfocusing. As a further advance, a couple of new beamforming structures are proposed for exploiting the new characteristics of NFC. 4) From the application perspective, new designs are discussed in the context of promising next-generation technologies in NFC, where our preliminary numerical results demonstrate that distance-aware target sensing and enhanced physical layer security can be realized in NFC. Finally, several future research directions of NFC are discussed.Comment: 9 pages, 5 figures, submit to possible IEEE journa